Various types of computers use touch screens to receive input from end-users. Generally, an end-user uses a finger or other instrument to make physical contact with the touch screen. The computer coupled to the touch screen detects the physical contact and reacts accordingly. While touch screens generally are adapted to detect input from a single finger or other instrument, they are often unable to properly detect and process simultaneous input from multiple such instruments. Further, touch screens require behind-screen circuitry that consumes an undesirably large amount of space.